1. Field
The present invention relates to an optical data storage medium capable of reversibly displaying information and a process of recording information for displaying on the medium.
2. Discussion of the Background
The importance of electronic data storage media in computer equipment for storing, recording and rewriting data has been increasing, in the office, home and in other environments. Such electronic data storage media include, for example, magnetic tapes; floppy disks; magneto-optic disks; compact-discs digital-audio (CD-DAs), compact disc-read-only-memory (CD-ROM), CD-Recordable (CD-Rs), CD-Rewritable (CD-RWs) and other compact disc (CD) media; digital video disc-read-only-memory (DVD-ROMs), digital video disc-recordable (DVD-Rs), digital video disc-random access memory (DVD-RAMs) and other DVD media; IC memory cards; optical cards; transportable hard discs and various other media. In addition, the types and volume of data stored in individual media have increased with increasing storage capacities. The demand has increased for optical data storage media in which data is stored and read by means of lasers.
Descriptions and volume names for the data stored in electronic data storage media are recorded as user readable indexes for the data. For such index recording, conventionally, an index label in the form of a sticker is applied onto a disc cartridge. For example, Japanese Laid-Open Patent Application (referred to as JPA, hereinafter) No. 9-282836 proposes a process of rewriting and displaying information as indexes for the stored data by using a liquid crystal/polymer composite film as an index label. In compact discs, however, the CD itself is separately used without a cartridge; if such a liquid crystal/polymer composite film is provided on the surface of the disc, the rotation of the disc is adversely affected and data might not, be reliably read or written by a laser light.
CD-ROMs, on which data have already been recorded in a production process, are used as read-only optical data storage media. In the case of CD-ROMs, indexes or various design patterns indicating the contents of stored data are printed on their protective layers with an ultraviolet-curing ink or an oil-based ink. Such indexes or design patterns are generally printed by screen printing, offset printing or other printing techniques, which are suitable for rapidly and efficiently printing the same pattern in a so-called mass printing process.
Write-once-read-many optical data storage media, such as CD-Rs, on which data can be recorded by a laser only once and the recorded data can be reproduced with a CD player, have been developed, and users have stored their own data for personal use, such as music and computer data, on CD-Rs. The CD-Rs generally have no description or only have some common characters or design patterns on their surfaces printed with an ultraviolet-curing ink or an oil-based ink. For adding description for such data for personal use, there have been proposed a process of writing the description as an index or other design patterns on a protective layer of the medium with an oil-based felt-tipped pen, for example, a process of applying a thin label onto the medium for writing the description thereupon, a process of providing an ink-accepting layer on the surface of a medium and recording the description by an ink-jet recording method (JPA-5-238005) and a process of providing a dye-accepting layer on the surface of a medium and recording the description by a sublimation thermal transfer recording process (JPA-8-48080). Each of the above processes may be carried out before or after optically recording personal data on an optical data storage medium.
Recently, optical data storage media in which stored data can be rewritten by a laser, such as CD-RWs, have been developed and come into use. When indexes or design patterns are recorded on the surface of these CD-RWs with a felt-tipped pen, by ink-jet recording or a thermal transfer recording method as in CD-Rs, such indexes or design patterns cannot be conveniently changed when the stored data is changed. In this case, the stored data can be inconsistent with the indexes and design patterns printed on the surface of the CD-RWs and hence the contents of the stored data cannot be easily recognized by the indexes and design patterns. When a thin label such as used in CD-Rs is applied onto these CD-RWs, and later the label is replaced with another label in accordance with changes of the stored data, the media may be scratched or otherwise damaged.